The Principles of Base Isolation and Seismic Protection of Structures

This chapter explains the principles of seismic isolation, starting with the representation of the seismic action through the elastic response spectrum of the structures. The elastic response spectrum is the diagram that contains all the information useful to the designer for designing the structure. In fact, the response spectrum contains information relating to the intensity of the earthquake, the conformation of the ground and its resistance, and the capacity of the structure or anti-seismic devices to dissipate energy. By observing the conformation of the response spectrum, it is then possible to easily deduce the possible strategies to reduce the effects of the earthquake: the increase in the period of the structure and the dissipation of energy. The concepts of damping, critical damping, and equivalent viscous damping, as well as the effect of the latter in reducing earthquake effects are also explained.